The known method for the preparation of a scintillographic agent, which is a derivative of iminodiacetic acid chelated with technetium 99 m Tc, comprises treating 2,6-diethylaniline or 2,6-dimethylaniline dissolved in acetic acid with chloracetyl chloride at a temperature of 10.degree. C. and then with a solution of sodium acetate. The mixture is shaken for 30 minutes. The resulting sediment is dissolved in a benzene diethylamine solution and this solution is warmed during several hours under a water circulation cooler. Hereafter the diethylamine hydrochloride is separated and the solution is extracted with hydrochloric acid. Then alkali is added to the extract which is extracted with ether. The obtained ether solution is distilled and the product of distillation is .omega.-chlor-2,6-diethylacetanilide. The yield in this process is about 70 %. Further, the .omega.-chlor-2,6-diethylacetanilide together with the sodium salt of iminodiacetic acid is dissolved in 75 % alcohol. The mixture is warmed during about two days under a water circulation cooler and, after evaporating the solvent, the dry sediment is dissolved in water and twice extracted with ether. After removing the ether extract, hydrochloric acid is added until pH reaches about 3.2 and the precipitated sediment is crystallized from water. The derivative of the iminodiacetic acid, produced in this way, is once more dissolved in water and, after the addition of stannous chloride in 1 n hydrochloric acid the pH value is adjusted to about 5,5 by the addition of sodium hydroxide. The solution is then clarified through a sterile filter, freeze-dried and stored in sterile ampoules fixed in nitrogen or filled at a reduced pressure. Just before an intravenous administration a sterile pertechnetate 99 m Tc solution is added to the derivative of the iminodiacetic acid. The durability of the scintillographic agent produced in that way is 6 hours.